Canis ISSN: 2398-2942

Synovial fluid: cytology

Contributor(s): Kathleen P Freeman, Jane Miller

Overview

  • Synovial fluid is a dialysate of blood and normally has a low white cell count (<2 x 10*9/l or 100 - 1000/mm*3 or <1000/ml) with minimal erythrocytes.
  • Refractometer protein is usually <2.5 g/dl.
  • Some reports indicate <3000/ml may be within normal limits in dogs.
  • A differential white cell count Synovial fluid: differential cell count and viscosity will help to distinguish inflammatory from non-inflammatory conditions.

Sampling

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Tests

Methodologies

  • Direct smear of drop as for blood smear.
  • For fluids of low cellularity:
    • Centrifuge at 100 rpm for 10 minutes.
    • Cytocentrifuge preparations or other special methods for concentration may be available at some commercial laboratories.
    • Pour off supernatant (care should be taken to observe specimen during pour-off since viscous synovial fluid may result in loss of sediment).
    • Flick tube to resuspend sediment.
    • Put 1 drop onto slide.
    • Make smear as for blood smear or pull apart/squash method using two slides.
  • Romanowsky-type stains most commonly used for cytologic evaluation.

Availability

  • Standard laboratory procedure.

Validity

Sensitivity

  • As with any cytologic specimens absence of evidence does not provide conclusive support for absence of a particular condition.

Specificity

  • As with any cytologic specimens absence of evidence does not provide conclusive support for absence of a particular condition.

Technique (intrinsic) limitations

  • Cytologic evaluation may be compromised by excessive blood contamination.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Gibson N R, Carmichaeal S, Li A et al (1999) Value of direct smears of synovial fluid in the diagnosis of canine joint disease. Vet Rec 144, 463-465.
  • Boon G D (1997) Synovial fluid analysis - a guide for general practitioners. Vet Med 92, 443-451.
  • Ellison R S (1988) The cytologic examination of synovial fluid. Semin Vet Surg 3, 133-139.

Other sources of information

  • Ettinger S J & Feldman E C (eds) (2000) Textbook of Veterinary Internal Medicine. 5th edn. Philadelphia: W B Saunders & Co.
  • Kaneko J J, Harvey J W & Brass M L (eds) (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Boston: Academic Press.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine. Clinical Pathology. 3rd edn. Iowa: Iowa University Press.


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